This invention relates generally to an endless track structure to replace wheels of a light, as well as other recreational vehicles, and more particularly to such a track structure that has a quick attachment method, a non-rigid movable frame and support method for both edges of an endless track.
The background of track structures for various wheeled vehicles have heretofore become known to adapt those vehicles for use on unstable and irregular surfaces, such as snow, sand, mud and irregular rocky terrain. Through the course of their development, many such devices have become known and their structures have become quite sophisticated to particularly adapt them to use under specialized conditions and with particular vehicles. In general such known track structures have been particularly designed for use with heavy massive vehicles of the automotive and truck type or two wheeled vehicles of the motorcycle type, undoubtedly because of the prevalence of such vehicles in commerce during the developmental period of track devices. Because most of such track devices have been specifically designed for use with a particular vehicle, this rather essentially has limited the use of these devices to those particular vehicles with which they were associated.
In the present day, three and four wheel recreational vehicles characterized by a small size and light weight, both substantially less than similar characteristics of an ordinary automobile, have become popular. Such vehicles normally are not designed for roadway use, but have traditionally been provided with pneumatic tires, commonly of a type to allow use of the vehicle on somewhat unstable and irregular natural surfaces, at least insofar as such use can be had with pneumatic tired vehicles. Pneumatic tires, however, or in fact any rotary type of wheels, do not allow effective use of such vehicles upon various unstable surfaces, such as loose snow of any substantial depth, unconsolidated earth, sand, mud, random spaced rocks and the like, which may be traversed readily by a track type vehicle. My current invention seeks to provide an improved track structure particularly adapted to replace wheels of such light wheeled recreational vehicles to allow vehicle use on unstable and irregular surfaces not adapted to traverse by pneumatic tires. The track structures heretofore used by heavy vehicles of an automotive or truck type have generally provided a rigid frame, bearing mounted drive cogs and idler wheels to define a course about which an endless track moves to support a vehicle on a surface for travel thereon. This type of rigid frame track structure has proven usable in heavier vehicles, especially when operated at low speed with a vehicle having a sophisticated suspension system to absorb shock. Such rigid frame track structures, however, are neither necessary nor desirable for use in track structures for light recreational vehicles and is not effectively usable with such vehicles. My invention provides a nonrigid movable frame that mounts spaced pairs of drive and idler wheels to define the course of an endless track. A primary feature of my invention provides a frame containing interconnected elastically deformable leaf spring elements. Either form of a movable frame allows relative motion between the driving self-cleaning cog wheels and various pairs of idler wheels supporting the endless track to absorb shock and maintain tension upon the track to keep it in its normal course and prevent accidental dislodgement, all to distinguish this frame from rigid frame structures which accomplish neither of these features. For a track structure that replaces pneumatic tires on a lightweight recreational vehicle to be practical, it must provide connecting methods that allow simple and easy installation or mounting on a carrying vehicle in a short time period by unskilled persons.
Previously known track structures have provided methods for releasable attachment to the existing hub structure of a vehicle that releasably mounts a wheel carrying a pneumatic tire. Most of those prior mounting methods have included an integral part of a track structure that either is not or cannot be easily removed to accommodate the mounting process, but rather the entire track structure has had to be mounted on the vehicle hub as a single unit. Some prior track structures have even had multiple support from the vehicle frame as well as a drive shaft. By reason of this, it has been commonly difficult to mount such track structures on a wheel hub because the track structure itself is large and heavy making it hard to position and to make access to the hub area difficult and inconvenient when the track structure is in position for mounting on a hub. Because of the difficulties in mounting, most prior track structures have usually been designed to be mounted for use for longer periods of time which is not desirable for light recreational vehicles as they are more desirable to change back and forth from wheels to tracks as the seasons or conditions would dictate. My invention solves this problem by providing a releasably interconnected shaft that is easily and simply removable from the track structure to allow the shaft to be separately mounted on a wheel hub with simple and easy access to the hub during mounting, and the endless track structure then reinstalled on the shaft after the shafts mounting on the hub. This feature distinguishes my invention from the prior art devices requiring mounting of an entire endless track device on a wheel hub as a single entity. Many prior track devices have provided particular driving cogs associated with particular endless tracks to drive those tracks from a medial position. This type of track structure has proven usable with heavier automotive type vehicles because of the weight of the vehicle, and especially when the vehicle has sophisticated suspension methods and is operated at relatively low speeds, but such structures are not well adapted for use with light recreational vehicles commonly without sophisticated suspension means and operated at higher speeds. The endless tracks used in all track structures have significant width and when they are driven from a medial position, especially at higher rates of speed, where is a substantial tendency, probably because of leveraged forces caused at the track edges, for the track to become dislodged from its normal course and eventually become separated from its support structure. My invention solves this problem by providing two spaced opposed driving cog wheels, with self-cleaning cogs on their interior peripheral surfaces facing each other, to provide simultaneous synchronous driving support for a track simultaneous at each of its side edges. This feature provides substantially more stability to maintain a track in its normal course and prevent accidentally loosening even at relatively high speeds. This structure also provides an additional benefit in allowing the use of track material that is presently available in commerce for use with ordinary snowmobiles, as such material commonly provides lug structures at its two side edges for driving support of the type required by my invention. Thusly existing endless track material and driving lugs presently commercially available, incorporating the latest state-of-the-art technology and lower cost in my invention.
Prior endless track structures generally have not been particularly concerned with the lower support course of the track because with heavier vehicles operating at relatively low speeds, the configuration did not cause any particular problem so long as there was sufficient track area to support the vehicle upon the surface over which it traversed. In this track structure, which is designed for use on light vehicles at relatively high speeds, it has been found desirable that the forward portion of the track course must be raised somewhat above the rearward flat portion, to help transfer the flexibility of the front portion of the track frame to the terrain and obstacles being traversed and also prevent the problem that the track will tend to accumulate and move snow, mud or debris in front of the track and the entire track structure will tend to move somewhat downwardly into a supporting surface. Either of such happenings will restrict motion of the track structure and tend to increase the probability of track dislodgement. Therefore the forward most pairs of idler wheels on the frame are at a spaced distance above the rearward pair of idler wheels defining the flat course of the track structure in its rearward part, and provide means to guide the track in a regular angulated course from the forward idler wheels to the rearward flat portion. Prior track structures generally have not provided any articulating or elastically resilient frame linkage between wheels defining the endless track course to aid in maintaining the track in a taut condition about its course. In general, this is not practical with heavier vehicles as the weight of the vehicles themselves would create too great a tension on the endless track to allow its effective operation. This invention, however, which operates on lighter recreational vehicles, does provide such linkage and in so doing is more efficient in maintaining the endless track in its normal course without dislodgement, especially at high speeds, than is the nonmovable frame structure of prior art devices. The particular type of movable frame structure of this invention also allows inclusion of traditional and special mechanical tension adjusting mechanisms to accommodate both a long term and short term changes or variations in belt length and tension. This invention resides not in any one of these individual features, but rather in the overall combination of all of the particular structures and functions necessarily included as herein set forth and claimed.